Sandy Hook, New Jersey, is one of New York Harbor's mellower pleasure grounds. A narrow, five-mile spit of rolling dunes and beaches that is part of the Gateway National Recreation Area, the Hook is just across the harbor from Manhattan and Coney Island--a deceptive proximity. While the canyons of downtown Manhattan resound with the sounds of a busy metropolis, and Coney Island echoes with the happy screams of roller-coaster riders, Sandy Hook's characteristic sound is the gentle chime of a fog bell that stands not far from the oldest working lighthouse in the country.

Between the Civil War and World War I, the nation's first army testing ground stood here, and its sands and soils are still rich with the remnants of nineteenth- and early twentieth-century military experimentation: shells of various sizes, the shrapnel that filled them, the fuses that set them off, and the gun barrels that fired them. "The technology that made our nation into a world power was all here," says Dana Linck, a former National Park Service archaeologist who until last fall worked extensively at Sandy Hook.

While the U.S. was busy disbanding its fighting forces in the aftermath of the Civil War, Prussia, France, and England made such enormous technological strides that they gave the Americans a serious military inferiority complex, says Joe Vann, a safety specialist with the U.S. Army whose expertise is the safe disposal of live ammunition. By the early 1870s, gripped by a deepening sense of military insecurity, the army established its first weapons testing ground at Sandy Hook. The United States spent years playing catch-up there, first on one proving-ground site, operational from 1874 to 1900, and then on a second, eight hundred feet south of the first. Until 1919, every single cannon the U.S. army either produced or purchased from private contractors stopped at Sandy Hook after leaving various foundries and before heading off to a coastal fort, going west for the Indian Wars, or shipping overseas to Panama or the Philippines. "They'd cast guns, take them to Sandy Hook, mount them, overload them, punch that big projectile down the beach, and do a good number of tests," says Linck. "If the gun didn't blow up, they could say it was proved."

Well over a hundred years after the United States army first began testing on Sandy Hook, the nation and the world are still feeling the reverberations of what was done there--in more ways than the obvious, historical one. Sandy Hook today is home not only to a National Recreation Area with a lovely beach and edifying historical plaques, but also to buried shells, including some potentially explosive ones.